Automatic transmissions generally include a plurality of torque transmitting mechanisms, such as clutches, brakes, or the like, which are selectively engageable and disengageable to change the operating mode, range or gear ratio of the transmission. The engagement and disengagement of the torque transmitting mechanisms are typically controlled by a control system that has electronic and hydraulic components.
In the control system, an electronic control issues signals to one or more electro-hydraulic actuators. The electro-hydraulic actuators also receive pressurized hydraulic transmission fluid from a fluid supply. The electro-hydraulic actuators output fluid pressure in accordance with control signals received from the electronic control and the supplied pressure. The actuators supply output pressure to fluid chambers of the respective torque transmitting mechanisms, either directly through a fluid passage or via a pressure regulating valve assembly.
There are a variety of different types of electro-hydraulic actuators that may be used to control the engagement and disengagement of the torque transmitting mechanisms, including on/off solenoids, pulse-width modulated (PWM) solenoids, and variable-bleed solenoids (VBSs).